For electronic mehatrons the second element of a designation is made of three letters: the first M - mehatron; the second letter corresponds to the
basic purpose of the device (in some designations mehatrons, developed earlier, this letter is absent); the third letter designates type of the device according to the list resulted above.

The third element - number, corresponding a serial number of the given type of a tubes.

P - in a glass environment, tiny (finger-type), diameter 19 and 22.5 mm;A - in a glass environment, supertiny, diameter
from 5 up to 8 mm;B - in a glass environment, supertiny, diameter from above 8 up to 10.2 mm;G - in a glass
environment, supertiny, diameter over 10.2 mm;S - in a glass environment, with a socle or without a socle, diameter more than 22.5
mm;N - in a ceramic-metal environment, tiny and supertiny;K - in a ceramic environment;D - in a metal-glass environment, with disks.

Tubes in metal to an environment of the fourth element of a designation no have.

Additional element. To a standard designation of a tube are sometimes added (after a hyphen) the letters describing special
properties of tubes, for example:

V - increased reliability and mechanical ruggedness (such as low susceptibility to noise and microphonics);R - even better than V, extra high reliability (10000 hours and more);E - extended service life (5000 hours and more);D - exceptionally long service life;I - optimised for "pulsed" (i.e. switching) mode of operation.

The third element consists of a dash ("-") followed by the design serial number. Letter can be used here in some special cases (GMI-6 – impulse modulator); if the tube has to be force-cooled, there might follow a letter A for water-cooled or B for air-cooled.

Popular transmitter tubes include the GU-29, GU-50, GM-70 and G-807 (the Russian 807 analogue).